A phase I/II trial evaluating long-term use of a Pediatric Robotic Exoskeleton (P.REX/Agilik) to improve gait in children with movement disorders

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Abstract

This is a study of pediatric outpatients with crouch gait from cerebral palsy (CP) or knee extension deficiency from another neuromuscular disorders such as muscular dystrophy (MD), spina bifida (SB), and incomplete spinal cord injury (iSCI). Individuals with CP walk in a crouched posture due to multiple impairments with motor control deficits being an important factor whereas patients with SB, MD or iSCI tend to exhibit gait pathology as a result of muscle weakness. Our study design will account for these identifiable differences underlying the mechanism of gait pathology, by separating participants by diagnosis into two subject pools for analysis: the CP subject pool and the Neuromotor Disorder subject pool (consisting of patients with SCB, iSCI or MD). The design of the study will be structured as a randomized, crossover study. The target intervention dosage will be constant across all participants (5 days/week, 1 hour/day). These two subject pools will complete the study design independent of each other including separate randomization into Groups A (who will receive the exoskeleton intervention first, followed by an observation period) and B (who will complete the observation period first, followed by the exoskeleton intervention) following inclusion in the protocol at visit 0. Both the CP and Neuromotor Disorder subject pools will complete the same study design, but will be analyzed independent of each other. The aim of the study is to investigate the safety and effectiveness of a robotic exoskeleton for overground gait training targeting improvements to knee angle profile, posture, and gait speed. As previous studies at the NIH have demonstrated the orthotic effects and immediate benefits of an extension-assist robotic exoskeleton on the target population of children with CP (protocol #13-CC-0210), this study will investigate longer-term benefits using this technology outside of the clinical setting and in application to a broader patient population including children and adults with knee extension deficiency from a diagnosis of SB, MD or iSCI. We hypothesize that use of a robotic exoskeleton for 1 hour/day, 5 days/week over a 12-week training period will lead to functional improvements in overground walking without the exoskeleton by (i) increasing peak knee extension angle, (ii) improving overground gait speed, and (iii) improving knee extensor, including the vastus lateralis and rectus femoris, muscle activation and strength. In addition, we hypothesize that regular use of a robotic exoskeleton over a 12-week training period will also improve volitional gait speed and the observed functional improvements in overground walking will persist following completion of the exoskeleton intervention training. This study is a single site outpatient study with testing to occur at the National Institutes of Health Clinical Center, Rehabilitation Medicine Department, Neurorehabilitation and Biomechanics Section. This is a study of a novel device. It is a pivotal study, analogous to phase 1, designed to assess both safety and effectiveness of the intervention. The robotic exoskeleton used as the intervention in this study consists of two orthotic braces, one for each limb, with each device containing a single robotically actuated degree of freedom at the sagittal plane knee joint (flexion/extension direction) and the associated embedded electronics and sensors to power and control the device. Additionally, and optionally, the robotic exoskeleton can incorporate a commercially available surface electronic stimulation device for stimulation of lower extremity muscles; the activation and timing of the electrical stimulation is integrated with the embedded control system of the exoskeleton. The study intervention device has 6 possible control modes for each participant (Table 4). With the ultimate intervention goal being increased volitional function following device use outside the clinical setting, our primary focus will be to establish a resistive or interleaved assistive/resistive mode for each patient to use for training to aid in rehabilitation of the knee extension deficiency. We aim to secondarily establish at least one assistive-only mode for training in the case the patient cannot operate under the resistive mode for the prescribed dosage of training. This is a multi-visit study with outcome assessments of the same measures at various points in the protocol. These measures include peak knee extension, knee extension at initial contact, step length, gait speed, knee moment, peak and mean activation of knee extensor and flexor muscles during walking, gross motor function classification system (GMFCS) categorization, pediatric evaluation of disability inventory-computer adaptive test (PEDI-CAT), gross motor function measure (GMFM-66), 6 minute walk test, timed up and go, modified Ashworth scale, Tardieu scale, and isometric strength test (Biodex) of knee flexion and extension. Recruitment for the study was initiated in May 2023, and to date three participants are currently enrolled, with 2 in Group A (exoskeleton intervention first) and 1 in Group B (observation first). Two participants are in the CP subject pool and one is in the Neuromotor Disorders subject pool.